It is common for vehicle engines to drive a plurality of accessories using an accessory drive system that includes a belt. In general, a tensioner is used to maintain tension on the belt, to inhibit belt slip during transient events and to inhibit the belt from coming off the associated pulleys of the driving and driven components.
In non-hybrid vehicles, the engine is the sole means of driving the belt and the associated components. Typically, one of the driven components in such a case is an alternator, which is driven by the belt to generate electricity that is used to charge the vehicle's battery.
In hybrid vehicles, a secondary motive device is provided for driving the belt. The secondary motive device (e.g. a motor/generator unit (MGU)) can be used for a number of purposes, such as, for example, driving one or more accessories via the belt when the engine is temporarily off while the vehicle is stopped for a short period of time (e.g. at a stoplight), a feature referred to as ISAF (Idle-Stop Accessory Function). Another purpose is for use as part of a belt alternator start (BAS) drive system, in which the MGU is used to start the engine via the belt. Yet another purpose is to supply additional power to the engine when needed (e.g. when the vehicle is under hard acceleration), referred to sometimes as a Boost mode.
In both non-hybrid and hybrid vehicles, particularly those with small engines, there is relatively little room for belt tensioners. Some manufacturers have attempted to fit tensioners to an end face of the frame of the alternator or MGU as the case may be, but with varying degrees of success. Such tensioners are sometimes arranged in a way that would interfere with other engine components in some instances, and would therefore be unusable on many engines. Other problems exist with certain examples of such tensioners. There is therefore a need for a tensioner that can at least partially address some of the shortcomings with currently proposed tensioners that are mounted to the MGU or alternator frame